JPH03210333A - Production of polyimide - Google Patents

Abstract

PURPOSE:To produce a polyimide without passing through an unstable polyamic acid stage by reacting an arom. diamine with an arom. tetracarboxylic acid (anhydride) in a solvent comprising a polyphosphoric acid. CONSTITUTION:A solvent comprising a polyphosphoric acids is prepd, e.g. by mixing phosphorus pentaoxide with water, with phosphoric acid, or with a polyphosphoric acid. In the solvent, an arom. diamine (e.g. 4,4'-diaminodiphenyl ether) is reacted with an arom. tetracarboxylic acid (anhydride) (e.g. 3,3',4,4'- biphenyltetracarboxylic anhydride) at 120-240 deg.C, pref. in an inert gas atmosphere.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention enables the direct synthesis of polyimide, which is a polymer having excellent heat resistance, chemical resistance, and mechanical properties, without going through the polyamic acid step. Concerning new manufacturing methods.

[Conventional technology]

Aromatic polyimides, such as DuPont's Kapton, are known for their excellent heat resistance, chemical resistance, and mechanical properties. These polyimides are usually produced in two steps: synthesizing polyamic acid, which is a precursor of polyimide, forming it into a film or the like, and then converting it into polyimide. As the reaction solvent, dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, tetramethylurea, etc. are used.

However, the polyamic acid obtained as a precursor is unstable.

[Problem to be solved by the invention]

The object of the present invention was therefore to develop an advantageous method by which polyimides can be synthesized directly without going through unstable polyamic acids.

[Means to solve the problem]

Utilizing the excellent dehydration and dissolving power of polyphosphoric acid, the polymerization of heterocyclic polymers (polyoxazole, polythiazole, polyimidazole, etc.), polyketones, polysulfones, etc. can proceed effectively in polyphosphoric acid. Yes (known (e.g. Iwakura, Polymer 1. [, 130 (19
However, it was completely unexpected that polyphosphoric acid would be effective as a polymerization solvent in the polymerization of polyimide.

The polyphosphoric acid that can be used in the present invention is the same as the polyphosphoric acid that is generally used in the polymerization of heterocyclic polymers. As for the method of adjusting the polyphosphoric acid composition, for example, a method of mixing phosphorus pentoxide and water, a method of mixing phosphorus pentoxide and or-IJ phosphoric acid, a method of mixing phosphorus pentoxide and polyphosphoric acid, etc. can be used. is possible, and there are no particular restrictions.

The present inventors completed the present invention as a result of various studies to solve this problem.

The present invention is a method for producing polyimide by reacting an aromatic diamine with an aromatic tetracarboxylic acid and/or an aromatic tetracarboxylic acid anhydride, which is characterized by using polyphosphoric acid as a polymerization solvent.

Polymerization can be carried out by stirring the aromatic diamine and aromatic tetracarboxylic acid and/or aromatic tetracarboxylic acid anhydride in polyphosphoric acid, preferably under an inert gas atmosphere, for example in a nitrogen stream. The polymerization temperature is generally 120 to 240°C, preferably around 200°C.

Aromatic diamines that can be used in the present invention include those commonly used in polyimide polymerization, such as phenylenediamine; metaphenylenediamine; 4.4
'-diaminodiphenyl ether; 3,3'-diaminodiphenyl ether; 3,4'-diaminodiphenyl ether; 4,4'-diaminodiphenylmethane, and the like. These diamines can also be used as a mixture of two or more types, and the type of diamine is not particularly limited.

In addition to the above diamines, diamines synthesized in polyphosphoric acid can also be used as they are as monomers for polyimide polymerization. For example, an aromatic double-terminated diamine containing an oxazole ring is synthesized by reacting 2 moles of para-aminobenzoic acid with 1 mole of 3,3'-dihydroxy-4,4'-diaminobiphenyl in polyphosphoric acid. be able to. By adding a tetracarboxylic acid component to this reaction solution and polymerizing it, polyoxazoleimide can be obtained in one pot (see Example 5).

Furthermore, not only para-aminobenzoic acid but also other amine group-containing carboxylic acids and base component monomers used in the synthesis of heterocyclic polymers (e.g. 3,3'-dihydroxy-4,4'-
Besides diaminodiphenyl, 3.3'.

4.4'-Tetraaminobiphenyl;2,5-diamino-1,4-benzenedithiol; 4,6-diamino-1
, 3-benzenediol; 1.2.4.5-tetraaminobenzene, etc.), similar aromatic diamines can also be synthesized.

In addition, it is also possible to synthesize a heterocycle-containing oligomer having amino groups at both ends by combining an amino group-containing carboxylic acid, an aromatic dicarboxylic acid, and the above-mentioned base component, and use this as a monomer. Aromatic diamines produced using other reactions known to react in polyphosphoric acid can also be used in the polyimide polymerization of the present invention.

Furthermore, it is also possible to polymerize a system in which the diamine solution synthesized in polyphosphoric acid and the above-mentioned aromatic diamine are mixed with aromatic tetracarboxylic acid and/or aromatic tetracarboxylic acid anhydride. There are no particular restrictions on the combinations.

Aromatic tetracarboxylic acids or aromatic tetracarboxylic acid anhydrides that can be used in the present invention include those commonly used as acid components in polyimide synthesis, such as pyromellitic acid;
3″, 4,4′-biphenyltetracarboxylic acid; 3
, 3'', 4, 4'-diphenyl ether tetracarboxylic acid; 3.3', 4,4'-diphenyl sulfone tetracarboxylic acid, etc., their acid anhydrides, and mixtures of two or more of these are used, The structure of the tetracarboxylic acids is not particularly limited.

In any case, an important feature of the present invention is that an imide bond is directly formed between an ortho-position dicarboxyl group and an amino group in polyphosphoric acid as a reaction solvent.

〔Example] The present invention will be explained below with reference to Examples.

Example 1 84% polyphosphoric acid prepared by adding phosphorus pentoxide to orthophosphoric acid in a nitrogen atmosphere (the composition of polyphosphoric acid is based on the weight percent of phosphorus pentoxide when it is assumed that polyphosphoric acid consists of phosphorus pentoxide and water) ) to 40 g under nitrogen atmosphere.
．． 4'-diaminodiphenyl ether (OD A) 0
．． Add 87 g (0,00434 mol) and
Stirred at °C for approximately 30 minutes. 3.3' to this mixture.

4.4'-biphenyltetracarboxylic anhydride 1.28
g (0,00435 mol) was added thereto, and the temperature was raised to about 140''C and stirred for 1 hour.Then, the reaction was continued at 210''C for 13 hours.

After the polymerization was completed, the reaction solution was cooled, mixed with water, and washed with water several times using a household mixer. After neutralizing with an aqueous sodium hydrogen carbonate solution, the mixture was washed again with water using a mixer.

The logarithmic viscosity of the obtained polymer at 30°C was 0.
In a 5g/d1 concentrated sulfuric acid solution, it was 1.43. The IR spectrum of this polymer is shown in FIG. It shows the characteristic absorption of polyimide at 1780°, 1720°, and 1380 Kaiser.

Example 2 Polyimide was polymerized in the same manner as in Example 1, with a polymerization temperature of 190''C1 and a polymerization time of 46 hours, to obtain a polyimide with a logarithmic viscosity of 1.32.

Example 3 0.80 g (0,0074 m
ol) and pyromellitic anhydride 1.61 g (0,
0074 mol) was added and the temperature was gradually raised to 200°C.
The reaction continued for 15 hours. The system turned yellow and viscous. The IR spectrum of the polymer obtained by the same treatment as in Example 1 is shown in FIG. 1780.1730.1380 Kaiser shows characteristic absorption of polyimide.

Example 4 To 40 g of 84% polyphosphoric acid prepared by adding phosphorus pentoxide to orthophosphoric acid under a nitrogen atmosphere, 0.75 g (0,0069 mol) of bulk phenylene diamine was added under a nitrogen atmosphere.
) and pyromellitic acid 1.76 g (0,0069 m
ol) was added, the temperature was gradually raised to 190°C while stirring, and the reaction was continued at 190°C for 4 hours. After the polymerization was completed, the polymer was treated in the same manner as in Example 1, and the IR spectrum of the obtained polymer is shown in FIG. 1790.1730.1380 Kaiser shows characteristic absorption of polyimide.

Example 5 0.65 g (0,0031 mol) of 3.3'-dihydroxy-4,4'-diaminobiphenyl, 0.82 g (0,0060 mol) of paraaminobenzoic acid, and 40 g of 85% polyphosphoric acid were added under a nitrogen atmosphere. to 150°C
After stirring for 24 hours at 135°C, 3.3', 4
, 4'-biphenyltetracarboxylic anhydride 0.88
g (0,0030 mol) was added. The reaction temperature was gradually raised to 200"C and polymerization was carried out for 16 hours. The system became viscous and it was observed that it stuck to the stirring rod. 0,5 in
The logarithmic viscosity of the g/d1 sulfuric acid solution was 0.35.

The IR spectrum of this polymer is shown in FIG.

The NMR spectrum of the diamine synthesized and isolated without polymerization to polyimide in this reaction shows the weight, M
The following signals were given in SO.

6-Oppn+ (s+ 4) 11 amino groups)+ 6.
7ppm (d, 4)! , aromatic ring), 7.7 ppm
<s, 48. aromatic ring), 7.99H (d, 4H
.

(aromatic ring), 8.01) I) + l (S, 2B, aromatic ring) (blank space below this page) Reaction formula: [Effects of the invention] According to the present invention, excellent heat resistance, chemical resistance, and mechanical properties are achieved. It is possible to efficiently and easily obtain polyimide, which is a polymer having Furthermore, if polymerization can be carried out in a solution state, it becomes possible to form polyimide by spinning etc., and there is no generation of volatile substances such as water, which was a problem when imidizing after forming with a polyamic acid solution. Molded articles with good properties can be obtained.

[Brief explanation of drawings]

1 to 4 are graphs showing IR spectra of polyimides obtained in Examples 1.3.4 and 5, respectively.

Claims (1)

[Claims] Characterized by using polyphosphoric acid as a polymerization solvent,
A method for producing polyimide by reacting an aromatic diamine with an aromatic tetracarboxylic acid and/or an aromatic tetracarboxylic anhydride.